ROS production-related phenomena and biochemical reactions of the seaweed Ulva rigida in response to the effect of environmentally relevant Bisphenol A concentrations

Bisphenol A (BPA) is an extensively used synthetic compound that has causes various hazardous effects on aquatic primary producers. Research on BPA impacts on marine macrophytes and especially on Ulva spp. is limited. BPA-induced oxidative stress in Ulva rigida determined even at environmentally relevant concentrations (Low Effect Concentration, LOEC: 0.3 μg L^-1, Terminal Day, TD: 7) and it was higher on 7-11D. Increases in superoxide dismutase (SOD) and ascorbate peroxidise (APX) activities on specific days and concentrations may suggest the activation of an antioxidant mechanism in response to BPA-induced oxidative stress. On 1-5D, BPA-induced oxidative stress did not sufficiently activate SOD. On 7D at 0.1 μg L^-1, SOD activity decreases the Corrected Total Cell Fluorescence (CTCF) values to the control level, whereas at 0.3 and 1 μg L^-1, both enzymes may not be able to scavenge the oxidative stress. Protein content decreases, from 7D onwards at 0.3-3 μg L^-1, which may indicate oxidative injury in these biomolecules, as the antioxidant mechanism was unable to equilibrate the oxidative stress. Oxidative stress goes hand in hand with lipid peroxidation (malondialdehyde, MDA) at 0.3 on 7D and at 0.3-3 μg L^-1 on 3D The chlorophyll (Chls), pheophytin (Phs) and carotenoid (χ+c) contents decreased on 5D at 0.1-3 μg L^-1 of BPA (LOECs: 0.1 for Chls and χ+c, 1 μg L^-1 for Phs, TD: 5). BPA toxicity, based on the thalli surface area, seemed to be BPA dose-dependent and it was more pronounced at 3D (LOEC: 0.1 μg L^-1, TD: 3). U. rigida is among the most sensitive marine macrophytes against BPA, as it can cause adverse effects on various 'biomarkers', even at environmental concentrations.